import{
    INCREMENTCOUNT,
    DECREMENTCOUNT
}from '../constant/countConst'
//定义reducer的初如值
const init ={
    count:0
}
export default function countReducer (prevStata =init ,action){
    // console.log("reducer调用了",prevStata,action);
   
    //接受action对象的type和data
    const {
        type,
        data
    } =action;
// switch这个是全等判断
    switch(type){
        case INCREMENTCOUNT:
           return{
            ...init,count:prevStata.count + data
           };

           case DECREMENTCOUNT:
            return{
                ...init,count:prevStata.count - data
            }
    }
   
    return prevStata;
}